1. Field of the Invention
The invention relates to a process and to an apparatus for purifying waste water, which contains heavy metals, which are cathodically deposited and having at least one cathode and one anode.
The invention relates to the purification of solids-containing waste waters, such as sludges, watercourse sediments or dredger sludge.
2. Description of the Prior Art
Hitherto use has been made of physicochemical processes, such as precipitation, filtration, extraction and oxidation. The known processes are only partly able to satisfy and at a high cost the ever stricter requirements regarding the purification of such waste waters, particularly due to the lower legal limits for pollutants in waste waters and deposited precipitation products. The precipitates and/or filtrate must be dumped as special refuse. No further processing or reuse is possible. Another disadvantage of the known waste water purification processes is the generally necessary addition of chemicals for precipitating the heavy metal impurities, so that the waste volume and salt freight are increased.
It is known to use electrochemical processes for the recovery of precious metals and e.g. copper in production processes, in which corresponding solutions occur. However, the known processes are unsuitable for the purification of waste waters, which in general contain several heavy metals and have a complex composition, particularly solids-containing waste waters and on a major industrial scale, because they are generally only designed for smaller quantities and it is only possible to operate in a discontinuous therewith.